Two objects move in opposite directions with speeds 6 m/s and 12 m/s. What is their relative speed?

Introduction / Context:
Relative speed quantifies how quickly the distance between two moving bodies changes. In opposite directions, relative speed is the sum of the magnitudes of their speeds.

Given Data / Assumptions:

• v1 = 6 m/s.
• v2 = 12 m/s.
• Opposite directions.

Concept / Approach:
For opposite directions: v_rel = v1 + v2. For same direction: v_rel = |v1 − v2|. Here we use the former.

Step-by-Step Solution:

Verification / Alternative check:
In 1 second, combined closing distance = 18 m—matches the definition.

Why Other Options Are Wrong:
6 or 12 m/s would be same-direction or single-speed interpretations; 15 or 20 m/s are arbitrary sums/differences.

Common Pitfalls:
Subtracting speeds when they are opposite; forgetting absolute values for same-direction cases.

Final Answer:
18 m/s